Forming apparatus for precambered metal sections

ABSTRACT

A forming apparatus ( 50 ) includes a roll former ( 51 ) operative to roll form a metal strip ( 100 ) to form a profiled metal section ( 10 ) of generally C section profile including a pan ( 12 ) and a pair of upstanding edge margins ( 14  and  16 ). The section profile incorporates a longitudinal precamber which is introduced by the forming apparatus by incorporating a prestretching apparatus ( 52 ) upstream from the roll former ( 51 ), and a bending apparatus ( 53 ) located downstream of the roll former ( 51 ). The prestretching apparatus differentially stretches the metal strip ( 100 ) in its longitudinal direction so as to form portions ( 101, 102 ), which are more elongated than a laterally adjacent portion ( 103 ) of the strip ( 100 ). The differential stretching compensates for longitudinal shortening of the metal strip in forming the profiled section in the roll former ( 51 ). The bending apparatus ( 53 ) uses a (3) point bending process and includes a reaction stage ( 60 ), a fulcrum stage ( 61 ), and an action stage ( 62 ). The action stage ( 62 ) which induces loading onto the profiled section ( 10 ) so as to bend the section about the fulcrum stage ( 61 ) is incorporated with the shearing assembly. A method of forming a metal section from sheet metal strip is also disclosed. In a further aspect a shearing assembly is disclosed which is height adjustable and which also includes a cutting element ( 77 ) and shearing block ( 78 ) which are pivotally mounted to an assembly frame ( 74 ).

TECHNICAL FIELD

The present invention relates to an apparatus for and method of, forminga metal section from sheet metal strip. The invention has been developedespecially for roll forming metal profiles such as metal decking and theinvention is herein described in that context. The invention however hasbroader application and is not limited to that particular use.

BACKGROUND OF THE INVENTION

Composite structures formed from metal decking on which a concrete slabis cast are commonly used in building. Typically, the decking isinstalled on site so as to span supporting elements, such as columns orwalls. The decking includes a pan section and upstanding edge regionswhich are in abutting relationship so as to form a continuous surface.Concrete is cast over the surface so that the upstanding edges areembedded in the slab. The metal decking therefore acts both as formworkfor casting of the slab, and also provides tensile strength to thestructure on curing of the slab.

In the applicants' earlier International applications, PCT/AU01/01446,and PCT/AU01/01447, an improved metal decking is disclosed whichincorporates a precamber in the longitudinal direction of the decking.The purpose of the precamber is to compensate for deflection of thedecking on casting of the slab thereby enabling the decking to spangreater lengths without exhibiting excessive deflection of the compositestructure. The decking in these earlier applications also discloses animproved edge interlock arrangement which further improves the strengthof the composite structure.

Whilst metal decking according to the above form has improvedperformance, difficulties have been encountered in incorporating theprecamber into the metal section.

SUMMARY OF THE INVENTION

Accordingly, in a first aspect invention relates to a method of rollforming a metal section from sheet metal strip comprising of the stepsof;

-   differentially stretching the metal strip in its longitudinal    direction so that at least one portion of the metal strip is more    elongated than a laterally adjacent portion of the strip;-   roll forming the differentially stretched metal strip to form a    profiled section; and-   bending the profiled section so as to introduce a longitudinal    precamber in the profiled section.

An advantage of the present invention is that the profile and precambercan be introduced into the section in a single pass. Furthermore, themethod can be easily introduced into an existing roll forming linemerely by including additional processing stations.

The applicants have found that by preconditioning the metal stripthrough differential prestretching, the amount that the metal sectioncan be bent without buckling of the section, or introducing significantareas of weakness in the metal section, can be significantly increased.

In one form, the metal strip is differentially stretched continuously ina longitudinal direction of the metal strip, so as to producelongitudinally extending elongated portions in the metal strip.

In one form, the differential stretching is designed at least in part tocompensate for the tendency of some parts of the metal section toshorten longitudinally as a result of lateral bending during rollforming of the metal strip.

In formation of a metal sections having shaped flanges that project inone direction form a web, the metal section tends to bow longitudinallyinwardly, with its centre of curvature on the opposite side of the webto which the flanges project. This occurs because rollforming to shapethe flanges results in longitudinal shortening of the flanges. Thedifferential stretching is designed to compensate at least in part forthe tendency of the bent sections of the metal strip to shortenlongitudinally so as to cause the metal strip to bow. This bending ofthe profiled section is about the face opposite to that in which theupturned edges of the section extend.

In one form, the metal strip is stretched in portions that are stretchedto induce the required precamber in the final roll formed product.

In one embodiment, the metal strip is roll formed so as to bedifferentially stretched.

In one form, the profiled section is caused to bend about a fulcrum tointroduce a longitudinal precamber. In one embodiment, the profiledsection is restrained upstream from the fulcrum and is caused to bedeflected from the roll forming line downstream of the fulcrum. In thisarrangement, a three point bending process is formed to introduce thelongitudinal precamber.

In one form, the apparatus to shear the profiled section into discretelengths is used as part of the three point bending process. In one form,the shearing apparatus is adjustable so that it can be set to cause theprofiled section to be deflected from the general line of the rollformer. In that arrangement, the metal section at the shearing apparatusis inclined to the line of the roll forming. In a preferred form, thecutting surface of the shearing apparatus can be similarly inclined sothat the shearing action remains perpendicular to the metal section.

In a further aspect, the invention relates to an apparatus for forming ametal section from sheet metal strip, the apparatus comprises:

stretching apparatus which is operative to differentially stretch themetal strip in its longitudinal direction so that at least one portionof the metal strip is more elongated than a laterally adjacent portionof the strip;

rollforming apparatus operative to roll form the differentiallystretched to form a profiled section; and

bending apparatus operative to bend the profiled section so as tointroduce a longitudinal precamber in the profiled section.

In a further aspect, the present invention relates to a shear assemblyfor use in cutting a profiled metal section, the shearing assemblycomprising an assembly frame, a shearing block attached to the frame andoperative to receive the profiled metal section, and a cutting elementwhich is moveable relative to the shearing block; wherein the shearingassembly is height adjustable so that the relative height of theshearing block can be adjusted and the angle of the cutting elementrelative to the frame can be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

It is convenient to hereinafter describe an embodiment of the presentinvention with reference to the accompanying drawings. The particularityof the drawings and the related description is to be understood as notsuperseding the generality of preceding the broad description of theinvention.

FIG. 1 is a schematic perspective view of metal decking for use in acomposite structure;

FIG. 2 is a schematic side view of an apparatus performing the metalsection of FIG. 1;

FIG. 3 is a detailed perspective view of a prestretching apparatus inthe system of FIG. 2;

FIG. 4 is a front elevation of the-prestretching apparatus of FIG. 3;

FIG. 5 is a side elevation of the prestretching apparatus of FIG. 3;

FIG. 6 is a front elevation of a reaction station in the rollformingsystem of FIG. 1; and

FIG. 7 is a front elevation of the fulcrum station of the system of FIG.1.

FIG. 8 is a side elevation of the action stage of the FIG. 1.

FIG. 9 is a front elevation of the action stage of FIG. 1.

FIG. 10 is a top elevation of the action stage of FIG. 1.

FIG. 11 is a front elevation of the action rollers of FIGS. 8, 9 and 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, a metal decking 10 is disclosed which is elongateand of generally C-section profile including a pan 12 and a pair ofupstanding edge margins 14, 16 respectively. The metal decking member 10in use is interconnected with a like member so as to form metal decking.The metal decking is designed with edge margins of one sheet abuttingthe other edge margins of an adjacently laid sheet and a concrete slabis cast onto the decking which embeds the upstanding edge margins 14 and16.

Each of the upstanding edge margins 14 and 16 include webs 15, 17 thatextend upwardly from the pan 12. Flanges 22,24 extend inwardly from anupper end of respective ones of the webs 15, 17 and includes arespective lip return 26, 28. One lip return 26 is turned back towardsits web 15, whereas the other lip return 28 is disposed generallyparallel to its web 17.

The web 15, 17 of edge margins 14 and 16 each include a respectivelongitudinally extending rib (30, 32). These longitudinal ribs areconfigured so that when adjacent decking members are laid, the rib 30,23 of one edge margin interlocks with the other web 30 of the adjacentdecking member to inhibit vertical separation of the metal deckingmembers 10. This interlocking of the ribs eliminates the need forfasteners to secure adjacent decking members together. In the embodimentshown, the ribs interlock through their complimentary shape so that oneof the ribs 30 resides within the other rib 32 of a decking member.

In addition, the pan 12 of the metal decking member 10 is longitudinallyprecambered about a bottom face 34 of the pan 12. The precamber of theweb is about 0.6% measured as the maximum longitudinal offset of the pan12 from a substantially flat plane and it is expressed as a percentagerelative to the length of the member 12. In a typical arrangement, thedecking member 10 is supplied in 6 metre lengths, and the maximum offsetlocated in the middle of the member 10 is about 35 mm.

In use, concrete is cast on an upper face 36 of the pan 12. Under theload of the cast concrete, the member 10 is caused to at least partlydeflect towards the flat plane under the significant weight of thisconcrete. The advantage of this longitudinal precamber is that itminimises the deflection from a flat line of the metal decking once theconcrete slab has been cast. As the maximum deflection is a criteria fordetermining the span lengths of the metal decking member 10, it allowsthe limit of the span length criteria to be extended. Another limitingfactor on the span length is the strength at the interlock of theadjoining upstanding region between adjacent decking members. The use ofthe ribs 30 and 32 increases the strength at this interlock. As a resultof the precamber and the increased strength at the interlock, the metaldecking member 10 is able to span to about 5 metres unsupported ascompared to spans of 3 metres for conventional decking member without alongitudinal precamber.

FIGS. 2 to 11 illustrate a forming apparatus 50 to make the deckingmember 10 from sheet metal strip 100. The roll former 50 both shapes thesection and incorporates the precamber.

The forming apparatus 50 includes a roll former 51 having series of 27rollforming stages which shapes the decking member 10. These rollformingstages are not the subject of the invention and are therefore notillustrated in any detail. The forming apparatus 50 also includes anadditional prestretching apparatus 52 located upstream of the rollformer 51, and bending apparatus 53 located downstream of the rollformer 51 and which precambers the member 10. Both these apparatus 52,53 are disclosed in more detail below.

Turning firstly to the prestretching apparatus 52 which is bestillustrated in FIGS. 3 to 5. The apparatus 52 is constructed as a singlestage device and is designed to differentially stretch the strip 100 sothat it includes longitudinally extended portions 101, 102 which aremore elongated than a mid section of the strip 103. The elongatedportions 101, 102 are located adjacent the edge margins of the strip 100in the area where the strip is subjected to maximum bending in the rollformer 51 in forming the profile. This prestretching apparatus 52 isdesigned to precondition the strip 100 so as to inhibit its tendency tobow about the upper face 36 of the metal decking member 10 which wouldotherwise occur during the rollforming. This tendency to bow upwardly iscaused by a relative foreshortening of the edge margins caused informing the upstanding edge margins 14, 16 of the member 10.

The prestretching apparatus 52 uses rollers 55, 56, 57, 58 and 59 todifferentially stretch the strip 100 as best illustrated in FIGS. 4 and5. These rollers are configured in a two over three arrangement and aredesigned so that they are disposed in the vicinity of the longitudinaledge margins of the strip 100. Further, each roller is tapered (as bestillustrated in FIG. 4) so that the amount of stretching varies acrosseach roller.

On exiting the prestretching apparatus 52, the strip 100 is then fedinto the rollformer 51. After passing through the stages of therollformer 51, the shaped metal profile 10 is then introduced into thebending apparatus 53 which bends the member 10 about its lower face 34.

To bend the member 10 to induce a precamber into the member 10, a threepoint bending process is used which requires that the bending apparatus53 includes three separate stages; a reaction stage 60, a fulcrum stage61, and an action stage 62. With this arrangement, the product isarranged to be bent around the fulcrum stage 61 whilst being supportedin the reaction stage 60. The action stage is height adjustable so thatit can be located below the line of the other stages of the roll former(51,52, 60 and 61) so as to introduce the bend into the member 10. Theamount of bending is dependent on the amount the action stage 62 isoffset from the line of the other stages of the roll former 50.

FIG. 6 illustrates the reaction stage 60 in more detail. In that stage,the member 10 is well supported with the pan 12 being captured betweenan infill roll 63 and floating block 64. The upper end 22, 24 of theupstanding margins 14 and 16 are in engagement with upper rollers 65 and66. This arrangement enables the profile 10 to be well supported and inparticular to resist any lifting of the web 12.

FIG. 7 illustrates the fulcrum stage 61. The fulcrum stage 61 includesan infill roller 67 and blocks 68. The pan 12 of the member 10 iscaptured below the roller 67 and blocks 68, as in the reaction stage 60.However, unlike the reaction stage 60, the upper ends of the margins 14and 16 are not restrained thereby allowing the member 10 to bend aboutthe infill roll 67. The bending is required to enable the profile tointroduce the required precamber.

In addition, the infill roll 67 in the illustrated form incorporates atapered surface 69 which tapers from a mid point 70. This tapered rollerintroduces a lateral precamber across the web 12 as illustrated in FIG.7. This lateral precamber may be retained in the final profiled section,but in the illustrated arrangement is only incorporated in this stage toassisting in forming the precamber. As the profiled section exits thefulcrum stage, the metal springs back so that it is generally flat as itenters the action stage 62.

In alternate arrangements (not shown) the infill roll 66 incorporates aflat surface that maintains a flat profile across the web 12.

FIGS. 8 to 11 illustrate the action stage 62. The action stage 62induces the loading on the member 10 that induces the bend to the memberat the fulcrum stage 61. This loading is resisted at the reaction stage60. The action stage 62 comprises a height adjustable table 71 with amounting plate 72 to which an action roll assembly 73 and shear frameassembly 74 are mounted. The height adjustable table 71 providesadjustment via a plurality of jack screws 75 which control the relativeheight of the action roll assembly 73 thereby allowing control of extentof curvature of the member 10.

FIG. 11 illustrates the action roll assembly 73. A pair of action rolls83, 84 both guide the member 10 into the shear frame assembly 74 andalso applies load to the member 10 to provide for bending the member 10.The spacing between the action rolls 83 and 84 can be adjusted throughadjustment bolts 85 to thereby cater for different sized profiles.

The shear frame assembly 74 houses a tilting shear assembly 76 comprisesan actuated blade assembly 77 and a reaction surface assembly 78. Theperpendicularity in the cutting of the member 10 is maintained by theshear assembly 76 being able to pivot on a bearing 79. The angle of tiltof the shear assembly 74 is able to be varied but is fixed in a selectedposition through the angular adjustment bolts 80 that are movable alongtheir axis relative to the shear frame assembly 74.

Fixed at the top of the tilting shear assembly 76 is a hydrauliccylinder (not shown) that actuates a moving blade 81. The reactionsurface assembly 78 has two fixed shear blades 82 that remove a section(slug) of member 10 when the moving blade 81 is actuated, wherein theremoved section is ejected via a chute 86.

In operation, metal strip is introduced into the apparatus 50 and isinitially prestretched (by apparatus 52), profiled (by the roll former51) and the then precambered (by apparatus 53), whereafter it is cutinto discrete lengths by the shear assembly 76. Accordingly, therollforming apparatus 50 provides a system where the metal strip can beprofiled and precambered in a single operation. Furthermore, theequipment required to the apparatus 50 to form the precamber in themember 10 may be easily introduced into an existing rollforming linemerely by including additional stages. Furthermore by preconditioningthe metal strip through differential prestretching, the amount the metalsection can be bent at the bending stage is increased without the riskof buckling of the section or introducing significant areas of weakness.With this arrangement, it is possible to introduce longitudinalprecambers in the order of 6% as advantageously used in the deckingmember 10.

In the claims which follow and in the preceding description of theinvention, except where the context requires otherwise due to expresslanguage or necessary implication, the word “comprise” or variationssuch as “comprises” or “comprising” is used in an inclusive sense, i.e.to specify the presence of the stated features but not to preclude thepresence or addition of further features in various embodiments of theinvention.

Variations and modifications may be made to the parts previouslydescribed without departing from the spirit or ambit of the presentinvention.

1. A method of roll forming a metal section from sheet metal stripcomprising the steps of; differentially stretching the metal strip inits longitudinal direction so that at least one portion of the metalstrip is more elongated than a laterally adjacent portion of the strip;roll forming the differentially stretched metal strip to form a profiledsection; and bending the profiled section so as to introduce alongitudinal precamber in the profiled section, in bending the profiledsection to introduce the longitudinal precamber, the metal of theprofiled section is stretched, and the metal strip is differentiallystretched in portions that facilitate the stretching of the metal in theprofiled sections during the step of bending of the profiled section. 2.A method according to claim 1, wherein the metal strip is differentiallystretched continuously in a longitudinal direction of the metal strip,so as to produce longitudinally extending elongated portions in themetal strip.
 3. A method according to claim 1, wherein portions of themetal strip shorten longitudinally in forming the profiled section andthe metal strip is differentially stretched so as to compensate for thelongitudinal shortening of the strip in roll forming the profiledsection.
 4. A method according to claim 1, wherein the profiled sectionis of a generally C-shape having a pan section and upturned edge marginswhich extend from one face of the strip, and wherein the profiledsection is bent about the face opposite to that in which the upturnededge margins of the profiled section extend.
 5. A method according toclaim 1, wherein the metal strip is roll formed so as to bedifferentially stretched.
 6. A method of roll forming a metal sectionfrom sheet metal strip comprising of the steps of; differentiallystretching the metal strip in its longitudinal direction so that atleast one portion of the metal strip is more elongated than a laterallyadjacent portion of the strip; roll forming the differentially stretchedmetal strip to form a profiled section; and bending the profiled sectionabout a fulcrum so as to introduce a longitudinal precamber in theprofiled section, wherein the profiled section is restrained upstream ofthe fulcrum, and is loaded downstream of the fulcrum to induce bendingof the profiled section about the fulcrum.
 7. A method according toclaim 6, wherein portions of the metal strip shorten longitudinally informing the profiled section and the metal strip is differentiallystretched so as to compensate for the longitudinal shortening of thestrip in roll forming the profiled section.
 8. A method according toclaim 7, wherein in bending the profiled section to introduce thelongitudinal precamber, the metal of the profiled section is stretched,and wherein the metal strip is differentially stretched in portions thatfacilitate the stretching of the metal in the profiled sections duringthe step of bending of the profiled section.
 9. A method according toclaim 8, wherein the profiled section is of a generally C-shape having apan section and upturned edge margins which extend from one face of thestrip, and wherein the profiled section is bent about the face oppositeto that in which the upturned edge margins of the profiled sectionextend.
 10. An apparatus for forming a metal section from sheet metalstrip, the apparatus comprising; stretching apparatus differentiallystretching the metal strip in its longitudinal direction so that atleast one portion of the metal strip is more elongated than a laterallyadjacent portion of the strip; roll forming apparatus roll forming thedifferentially stretched strip to form a profiled section; and bendingapparatus bending the profiled section so as to introduce a longitudinalprecamber in the profiled section, the bending apparatus comprising amultiple stage device including a reaction stage restraining the metalstrip, a fulcrum stage about which the profiled section bends, and anaction stage inducing a load on said profiled section to induce bendingof the profiled section about the fulcrum stage, the bending apparatusintroducing a three point bend to said profiled section.
 11. A formingapparatus according to claim 10, wherein the stretching apparatusincludes at least one roller engaging a portion of the metal strip andelongating the engaged portion of the strip.
 12. A forming apparatusaccording to claim 11, wherein the at least one roller has a taperedsurface so as to vary the amount of stretching across said engagedportion of the metal strip.
 13. A forming apparatus according to claim10, wherein the action stage is height adjustable relative to thefulcrum stage enabling the amount of precamber introduced into theprofiled section to be varied.
 14. A forming apparatus according toclaim 10, wherein the action stage includes a shearing assembly cuttingsaid profiled section in discrete lengths.
 15. A forming apparatusaccording to claim 14, wherein the shearing assembly comprises ashearing block receiving the profiled metal section, and a cuttingelement moveable relative to the shearing block, the shearing assemblyand the action stage mounted to a common height adjustable assemblyframe.
 16. A forming apparatus according to claim 15, wherein thecutting element is angularly adjustable relative to the frame.